二维硅烯材料及器件的界面调控机理研究

Silicene is a stable two-dimensional (2D) buckled honeycomb lattice of silicon atoms that recently has been attracting substantial interest owing to its unique solid-state properties which are gradually coming to light. Its compatibility with ubiquitous Si technology offer the real prospects of greater transformational impact than graphene and other 2D layered materials. Much of its unique and novel properties arise from its buckled layered structure. This structure consists of mixed sp2-sp3 bonds , which is in stark contrast to the sp2 planar structure of graphene or the sp3 diamond-lattice bulk silicon. Monolayer silicene is expected to be a very useful and potentially breakthrough material for optoelectronics for several reasons including: i) field-induced inversion symmetry breaking for non-linear χ(2) electro-optic effects, ii) tunable small direct bandgaps (~≤0.3eV) by a vertical field in a single monolayer for broadband optoelectronics, iii) large direct bandgap (~0.8eV) opening by functionalization with hydrogen, fluorine, and polymer functional groups for mid-infrared and conventional communication optoelectronics, iv) substrate interface enhanced bandgap and band structure, and v) compatibility with Si technology for integrated Si photonics. In addition, recent theoretical studies have uncovered several novel phenomena including the quantum spin Hall effect, piezomagnetism, giant magnetoresistance, and enhanced optical absorption compared to graphene. In light of the substantial interest in silicene, there are however, very limited experimental results, and no demonstrated silicene devices to date due to several challenges that need to be resolved. .This research effort seeks to pioneer material study of silicene surface stability based on innovative growth approaches and systematic elucidation of the degradation kinetics. In addition, real-time characterization on the degradation of fabricated silicene devices will be experimentally investigated for the first time in order to shed light on the optoelectronic properties and device physics.

最新涌出的翘曲二维材料适用于研发新型或改良的微电子，光学及化学感应器，对于日常生活和国土安全都有着重要意义。 硅烯是由硅原子组成的类石墨烯结构的二维翘曲单原子层膜，且与主流半导体工业技术有着天然的材料和工艺相容匹配度和独一无二的无缝技术转化前景。相比于众多的理论与计算研究，硅烯实验研究则远远落后。主要原因是因在常温常压下的不稳定性。申请人提出了氧化铝/硅烯/银薄膜三明治封装的方法来暂时稳定硅烯的界面，从而首次实验上制得硅烯晶体管器件并成功观测到与理论预期一致的双极性载流子电传输现象【见2015年2月《自然-纳米技术》一作文章】。尽管如此，硅烯材料或器件在去银后的迅速失稳仍是阻碍实验研究前进的绊脚石。本项目针硅烯研究中的这个瓶颈问题将展开涉及材料科学，表面物理化学与器件物理的基础实验研究；以期理解硅烯界面与银和一些其它官能团相互作用的机理以及对电子声子能级结构的影响，从而寻得妥善的界面调控。

最新涌现的二维单质半金属半导体材料，如硅烯、磷烯，理论预计具有适中直接带隙和较高载流子迁移率，在中高频传感器、分子检测、能源装置等方面具有广泛的应用潜力。迄今为止，实验研究的主要挑战是如何在常温常压环境中保持这类二维材料的稳定性和本征性。本项目基于先前的硅烯三明治转移及封装工作，通过材料层数的精准控制和器件集成技术中界面物理化学调控两种方法，成功地提高了硅烯器件工作寿命1000多倍！取得了国际领先的硅烯器件工作，得到5次国际会议邀请报告。本项目还运用物相、表面和电学等综合表征方法，研究不同属性的分子薄膜对硅烯表面稳定性和本征性（如带隙及电学性能）的影响，探讨了其界面失稳的机理及相应的改善方案。研究取得的重要成果发表在高质量国际期刊（如影响因子>40的Chem Soc Rev），并多次在国内外学术会议上作邀请报告。该研究为开发基于硅烯二维半导体材料的新颖纳米器件应用提供重要科学线索和工程基础。